It shouldn't be hard to display squares around all units (and to be able to toggle them on and off).
That depends tho, It could be like in those games the reason they have a random banana there is because everything breaks without it, So maybe if this was added everything would collapse on itself.
I've already noticed a few oddities with the rendering engine or whatever it's called, (I can see the bottom sectors go black before they leave my screen, causing a weird effect.) and I don't know how much it's capable of handling.
This does sound simple to us, but we can't judge it until someone has actually tried putting it in to see if it would screw with the game.